Inner Mongolia has been well-known in the paleontological society by rich vertebrate fossils, however, there are few well developed sections with superimposition of fossil levels. Here the authors present the preliminary results of their field seasons during 2006~2009 in the Damiao area, central Inner Mongolia. The similar faunal community structure and continuity of main lineages suggest a relatively stable moderate humid and warm forest-grassland environment from the Early Miocene to early Late Miocene. The significant environment change seems to have happened after the earliest Late Miocene.